Crankshaft ablation, mainly by the crankshaft journal and shaft tile between the failure to form an effective lubricant film, making the crankshaft journal and shaft tile direct friction caused. When the diesel engine crankshaft ablation, will smoke, metal clash sound, and even cause the crankshaft and shaft tile hold together and can not turn. Therefore, the causes of the failure must be correctly analyzed and judged. 1. poor quality of oil 1) Poor quality of oil. The selected oil quality grade and viscosity grade is low, or different brands of engine oil for blending, resulting in the use of oil performance can not meet the requirements; oil use process mixed with a large amount of dust, as well as because the diesel engine operating temperature is too high, so that the oil oxidation degradation. The oxidized and deteriorated engine oil is black and lusterless, the concentration increases, and when you twist the oil with two fingers, it feels like there is dust and impurities in the oil. If you find the above phenomenon, you must replace the oil in time. 2) The oil becomes thin. As part of the diesel engine injection pump lubrication using pressure lubrication method, once the injection pump and lubricating oil channel seal failure. Diesel oil into the lubricating oil cavity, will make the diesel engine lubricating oil dilution deterioration. In addition, if the water jacket has cracks or grit holes, so that cooling water seeped into the oil will also make the oil thinner. Check the upper parts of the diesel engine (cylinder head upper plane, valve mechanism, cylinder head cover shell) for water vapor or water droplets. If you find that the oil volume increases, the concentration decreases, the viscosity decreases, and there is raw oil smell, it means that the oil is mixed with diesel oil. 2. The oil stock is not enough, the oil pressure is low Oil stock is not enough, oil pressure is low, will cause the diesel engine lubrication oil flow is not enough, and then can not ensure that the diesel engine crankshaft journal and shaft tile between the formation of lubricating oil film. Check the quantity of oil in the oil sump and the reading of the oil pressure gauge, and further check whether there is any blockage and leakage in the oil pipeline and other abnormalities. 3. crankshaft journal and shaft clearance is too large or too small 1) The crankshaft journal and shaft tile clearance is too large, resulting in low diesel engine oil pressure, unable to form sufficient lubricating oil film. 2) The crankshaft journal and shaft tile are too small because of the clearance, and the oil film thickness between the crankshaft journal and shaft tile is not enough or no lubricating oil film. When the clearance is too large or too small, use micrometer, measuring cylinder table to check the journal, bearing hole, shaft tile size, calculate the clearance, also can be used to directly measure the clearance with the plug ruler. 4. crankshaft or cylinder block geometry exceeds the size 1)The crankshaft radial runout is large, so that the journal and shaft clearance is small or no clearance, lubricating oil film thickness is not enough or no lubricating oil film. 2)The coaxiality of main bearing hole of cylinder block is too poor, resulting in the clearance between journal and shaft tile is too small or no clearance, and the thickness of lubricating oil film is not enough or no lubricating oil film. 3) The cylinder and the main bearing hole perpendicularity is poor, resulting in the connecting rod journal, main journal clearance is too small or no clearance, the thickness of lubricating oil film is not enough or no lubricating oil film. In the case of new or overhauled diesel engine put into use for a short period of time, the above phenomenon is often formed. Determine the geometry of the poor parts can first use the hand crank to shake the diesel engine crankshaft (rotating effort), and then cylinder by cylinder loose unloading diesel engine main bearing cover and connecting rod bearing cover, and then rotate the crankshaft. According to the size of its rotating crankshaft torque, the change in the difference to determine the specific (but to determine the size of the excess value, it is necessary to disassemble the diesel engine, with a special inspection tool to determine). 5. crankshaft journal, connecting rod journal shape and size of the excess Crankshaft journal, connecting rod journal or cylinder block main bearing hole, connecting rod big head hole cylindricity or taper difference, will make the journal and the shaft tile clearance intermittent (intermittent) or tapered. Can not ensure the formation of a better lubricating oil film. In the new machine or after overhaul diesel engine put into use not long, prone to the above phenomenon, can be measured on the journal size. If the measured journal ablation, can measure the adjacent corresponding journals (because under the conventional corresponding journals using the same equipment, the same cutting tool processing, so can represent the shape of the ablation journal error). 6. crankshaft main journal, connecting rod journal surface roughness exceeds the poor Due to poor roughness, there are many metal peaks on the surface of the journal, which destroys the integrity and continuity of the lubricating oil film between the journal and the shaft tile. Metal peaks directly with the shaft tile friction, resulting in crankshaft ablation. Failure often occurs in new or overhauled diesel engine into use for a short time. If the measured journal ablation, available roughness tester to measure the corresponding adjacent journal (because in general, the corresponding adjacent journal using the same equipment, the same cutting tool processing, so that the measured roughness can represent its ablation journal roughness). 7. crankshaft, flywheel, clutch dynamic balance is out of balance Dynamic balance is poor, crankshaft high-speed rotation inertia force, will make the crankshaft journal and shaft tile with the gap is damaged, serious will make the journal and shaft tile direct friction and cause crankshaft ablation. Failure generally occurs in the mechanical driving 10,000km later, crankshaft ablation can be removed after the residual debris on the journal, re-calibration dynamic balance, its unevenness can basically indicate its ablation journal dynamic balance over-balance amount. 8. Improper maintenance If the diesel engine is not reasonably maintained and serviced in time after running for a period of time, it will cause the parts such as oil pump pressure limiting valve to wear out and fail to deform. Oil filter element will be oil, sludge blockage, so that the oil pressure is reduced, causing crankshaft ablation.

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